0\; ,a>0\; ,a\ne 1\\\\log_3{x}=-4\; \; \to \; \; x=3^{-4}=\frac{1}{3^{4}}=\frac{1}{81}\\\\log_{x}{64}=6\; \; \to \; \; 64=x^6\; ,\; 2^6=x^6\; \; \to \; \; x=2" alt="log_{a}{x}=b\; \; \to \; \; x=a^{b}\; ,x>0\; ,a>0\; ,a\ne 1\\\\log_3{x}=-4\; \; \to \; \; x=3^{-4}=\frac{1}{3^{4}}=\frac{1}{81}\\\\log_{x}{64}=6\; \; \to \; \; 64=x^6\; ,\; 2^6=x^6\; \; \to \; \; x=2" align="absmiddle" class="latex-formula">